NEW YORK — FX is spinning off a new cable network aimed at young adult viewers.

Launching Sept. 2, FXX will join big brother FX along with the movie-oriented FXM. All three networks will share the same sensibility, FX Networks president John Landgraf said in making the announcement Thursday. It’s a mind set summed up by the brand’s new tagline, “Fearless.”

“All told, the three networks will air 25 original series in the next few years,” he added, calling that figure comparable to any of the major broadcast networks.

The lineup for FXX will consist of original series, movies and acquired series targeting adults 18 to 34, a slightly younger demographic than the 18-to-49 audience FX attracts, Landgraf said. FXX will initially be available in 74 million TV homes.

The new channel will be anchored by the comedies “It’s Always Sunny in Philadelphia” and “The League,” two veteran series that until now have originated on FX. In addition, “Legit” will move to FXX, as well as the FX late-night series “Totally Biased with W. Kamau Bell,” which will expand to a five-nights-per-week schedule.

Coming to FX this July is a new drama series titled “The Bridge.” Starring Demian Bichir and Diane Kruger, it centers on two detectives hunting down a killer operating on both sides of the U.S.-Mexican border. The pilot for another future series, “Tyrant,” will be directed this summer by two-time Oscar winner Ang Lee.

And FX’s first limited series will be “Fargo,” inspired by the acclaimed 1996 film of the same name.